Threadleaf ragwort

Senecio flaccidus, commonly called threadleaf ragwort or threadleaf groundsel, is a fast-growing, short-lived (3-6 years) bushy perennial subshrub in the Asteraceae family reaching approximately 1.4 m in height. The plant produces multiple slender, leafy, often grey-green stems clothed with narrow, deeply pinnately divided, nearly thread-like leaves up to 10 cm long, lending a feathery appearance. From April through September it bears showy bright yellow flower heads 3-4 cm across in loose terminal corymbs, each head with conspicuous ray and disc florets producing tufted wind-dispersed achenes. The species is native to central and southwestern North America from Utah and Kansas south into Arizona, New Mexico, Texas, and northern Mexico, occupying disturbed habitats, dry streambeds, overgrazed rangelands, and desert grasslands between 550 and 2,000 m elevation. The herbage contains the hepatotoxic pyrrolizidine alkaloids senecionine, retrorsine, and longilobine, rendering it poisonous to cattle and horses.